This invention relates to assays, and particularly to lateral flow assays in which a liquid analyte is applied to a sample zone of a test strip, allowed to migrate along the strip by capillary action, and detected in a capture zone.
Assays are frequently used to detect the presence of analytes in aqueous test samples in clinical and forensic medicine, and for environmental testing, food contaminant testing, and drug use testing. There is a growing demand for such assays that are based on reactions between specifically reactive substances, and that can be conducted outside of the laboratory setting, for example at home.
There are a number of over-the-counter (xe2x80x9cOTCxe2x80x9d) home testing and health care professional (xe2x80x9cHCPxe2x80x9d) diagnostic devices that can be used to collect human body fluids and perform diagnostic assays. An example of such a diagnostic device is a dipstick used for midstream urine sampling, such as found in pregnancy testing, or testing of urine from a specimen placed in a receptacle. Both OTC and HCP diagnostic devices can be lateral flow devices, in which a liquid specimen is applied to a sample zone of a lateral flow chromatographic test strip. The strip is usually made of a porous carrier material (such as nitrocellulose) so that the liquid travels along the strip by capillary action to an indicator zone, which indicates a presence, absence, or quantity of the analyte. Sometimes a wick is attached to the strip to help move the liquid specimen into or along the sample zone. Numerous lateral flow analytical devices have been disclosed, and include those shown in U.S. Pat. Nos. 4,775,636; 4,703,017; 4,861,711; 4,855,240; 4,857,453; 4,943,522; 4,945,042; 4,496,654; 5,001,049; 5,075,078; 5,126,241; 5,451,504; 5,424,193; 5,712,172; and WO92/12428; WO 94/01775; and WO 97/06439, each of which is incorporated by reference.
Many lateral flow devices are one-step lateral flow assays in which a biological fluid is placed in a sample area on a bibulous strip, and allowed to migrate along the strip until the liquid comes into contact with a specific binding partner that interacts with an analyte in the liquid. Once the analyte interacts with the binding partner, a signal (such as a fluorescent dye) indicates that the interaction has occurred. Multiple discrete binding partners can be placed on the strip (for example in parallel lines) to detect multiple analytes in the liquid. The test strips can also incorporate control indicators, which provide a signal that the test has adequately been performed, even if a positive signal indicating the presence (or absence) of an analyte is not seen on the strip.
Although lateral flow devices have been widely used in clinical practice, there are still obstacles to both clinical and home use because of the difficulty obtaining some specimens (such as blood), or the reluctance of users to collect certain specimens (such as urine). Even in situations in which urine tests are widely used (such as urine analysis for drug testing), it can be awkward or distasteful to obtain the specimens for analysis. Moreover, it is sometimes difficult to positively identify a specimen as coming from a particular individual, because of the possibility that specimens have been mislabeled or exchanged after collection but before testing.
U.S. Pat. No. 5,910,122 (D""Angelo) discloses a saliva collector which encases a tip of an aspirating pipette, for subsequent analysis in a separate test. U.S. Pat. No. 5,380,492 shows another saliva collector which incorporates an indicator in the collector that changes color when sufficient saliva has been collected. U.S. Pat. No. 4,635,488 is a body fluid sampling device which has an absorbent nib that collects saliva and conducts it to an analysis element in an interior of a tube. The analysis element can be placed in the tube after saliva collection is completed. Alternatively, liquid communication between the nib and analysis element is altered by a porous, absorbent but hydrophobic disc that conducts the saliva to the analysis element after being wetted with a wetting agent.
A problem that has retarded the more widespread use of intra-oral collection devices is that regulatory agencies and test subjects have been concerned about the reverse migration or reflux of detection reagents from the device into the mouth. Such reflux could cause a test subject to experience a noxious taste, or even carry potentially harmful detection reagents into the mouth of the subject.
Many lateral flow tests are used for regulatory or legal purposes, and proper identification of the test subject is important. Prior devices have included a label on which identifying information can be written (for example, in U.S. Pat. No. 5,380,492). However, incorrect information can be intentionally or unintentionally entered on such labels.
It would be advantageous to provide a simple and convenient assay that is suitable for home use, avoids reflux of test reagents, and/or which can readily identify a person from whom the biological specimen is obtained.
The present invention is a lateral flow device for analyzing analytes in a liquid, such as drug metabolites in saliva. In some of the disclosed embodiments, the lateral flow device includes a collection member which communicates with a lateral flow member that includes test result indicators which signal the presence, absence and/or quantity of analytes in a test liquid. The collection member absorbs or adsorbs a liquid (such as saliva in the mouth) to which the collection member is exposed. A removable barrier between the collection member and the lateral flow member inhibits the flow of liquid from the collection member when the removable barrier is present, but permits the liquid to flow into and through the lateral flow member when the barrier is removed. In some embodiments, a sufficiency indicator may be displayed by the collection member to indicate when a sufficient amount of saliva has been collected to remove the barrier.
In particularly disclosed examples, the barrier may be a negative barrier or a positive barrier. A positive barrier is a substantially liquid impermeable barrier, for example a substantially liquid impermeable plastic sheet. In some embodiments, the lateral flow member overlaps the collection member or abuts it in end to end contact, and the removable barrier may be a removable spacer interposed between the collection member and the lateral flow member. Alternatively, the liquid impermeable barrier may be a negative barrier, such as a gap between the collection member and the lateral flow member. Instead of removing such a barrier, the gap is closed, for example by sliding the collection member and the lateral flow member into contact with one another. In a particularly disclosed embodiment, the collection member and lateral flow member slide into an overlapping contiguous relationship.
The present device may be used for collecting oral secretions for subsequent analysis. A particularly suitable intra-oral device includes a housing that holds the lateral flow member and at least a portion of the collection member, with the collection member extending outside of the housing for placement in the mouth. The removable barrier may be contained within and accessible from outside of the housing, to permit the removable barrier to be removed from the between the collection member and lateral flow member when sufficient oral secretions (such as saliva) have been collected. The housing may define one or more windows though which the test result indicators can be viewed on the lateral flow member. It my be advantageous to close the windows, with clear or magnifying materials such as glass or plastic, to help isolate the interior of the housing from the oral environment.
The housing may also include slots through which a portion of the barrier extends to an exterior of the housing. An interior portion of the barrier is interposed between the collection member and the lateral flow member, so that the external portion of the barrier may be grasped and pulled out of the housing to permit the collection member and lateral flow member to come into contiguous liquid transferring contact. Alternatively, when the barrier is a negative (e.g. gap) barrier, a sliding member may move either or both of the collection member and lateral flow member into overlapping or other contiguous contact.
When the housing is intended for insertion into a body orifice (such as the mouth), it is particularly advantageous for an anterior portion of the housing to taper toward the collection member to be more comfortably retained in the orifice. Hence when the collection member extends anteriorly out of the housing, the housing tapers in that same direction to facilitate insertion of the device into the liquid collection orifice (such as the mouth). In some embodiments, the housing also has substantially flat top and bottom surfaces, and a low profile, to fit comfortably between the dentition of a test subject.
In other embodiments, multiple lateral flow members can be used instead of a single such member. For example, two lateral flow members may be opposed back to back, in communication with a single oral collection member. A removable substantially liquid impermeable positive or negative barrier may be present between the collection member and both of the lateral flow members. Removal of the barriers allows test liquid to flow from the collection member into both of the lateral flow devices. When the lateral flow members are opposed back to back, the test results of both strips can easily be read in situ (without removal from any housing) by viewing opposite faces of the housing. However, more than two lateral flow members can be arranged in a variety of configurations, for example in a triangular or quadrilateral array.
A physical identifier region may be present on the device to interact with and identify the user. The physical identifier region may be a segregated fingerprint receiving region, such as a relatively smooth, segregated area on the housing at a position that a digit (such as a thumb) of a test subject would grasp the housing to insert it in the mouth.
In a more particular embodiment, the device includes an elongated housing having dimensions that allow the housing to be placed in a mouth of a subject. A lateral flow chromatography member is contained within the housing, and a collection member is positioned to contact the lateral flow chromatography member. The collection member is elongated and extends to outside of the housing for insertion and retention in the mouth of a subject, and a removable barrier is present between the collection member and the lateral flow chromatography member, to interrupt movement of liquid between the collection member and the lateral flow chromatography member when the barrier is in place. The collection member and the lateral flow chromatography member are both elongated and longitudinally overlap, and are spaced from one another by the removable barrier, which is substantially impervious to any liquid, regardless of the chemical characteristics of the liquid. The housing defines an access opening though which the removable barrier is accessible for removal. The barrier is a liquid impervious sheet that extends between the collection member and the lateral flow chromatography member along a region of overlap between the collection member and the lateral flow chromatography member. An external portion of the barrier material extends through the access opening in the housing, to the exterior of the housing, so that the external portion can be grasped outside of the housing and pulled out of the housing to remove it. Once the barrier has been removed, the collection member and lateral flow member become contiguous. A bias member, such as a resilient pad, may bias at least one of the collection member or the lateral flow member into contact with one another, to improve contiguous contact between them after the barrier is removed. A window in the housing allows a test result indicator to be viewed without removing the lateral flow chromatography member from the housing.
To help assure that an adequate amount of liquid has been collected by the device before the barrier is removed, a soluble sample adequacy indicator (such as a dye) may be present on the lateral flow member. The indicator is solubilized by the collected liquid, and migrates along the collection member with liquid collected by the collection member. This flow moves the sufficiency indicator to a pre-selected position on the collection member, so that the sufficiency indicator can be viewed through a window in the housing once the pre-selected amount of liquid has been collected by the collection member. The housing may also include a liquid port through which substances can be introduced through the housing on to the lateral flow member and/or the collection member.
Any of the embodiments of the device may also include a wicking member in contact with the lateral flow chromatography member. The wicking member may be positioned to draw liquid from the collection member through the lateral flow member. For example, the wicking member may be a highly absorbent material contiguous with the lateral flow member, at a proximal and/or distal region of the liquid flow path from the mouth through the lateral flow member.
Particular embodiments of the lateral flow member include one or more analyte indicator agents that interact with an analyte in the liquid to provide a test result (such as a color change in an indicator line). Many different indicator agents may be used, such as a capture agent which captures an analyte. The capture agents may be a binding partner, such as an antibody, for example a monoclonal or polyclonal antibody. The indicator agents may be arranged in a series of indicator lines which detect different analytes. The indicator agent may provide an optical, electrical, or magnetic signal to indicate a presence of an analyte in the liquid.
The disclosed device therefore provides a two-step lateral flow device, in which the first step is collection of liquid into the collection member, and the second step is elimination of the barrier. The device can be used in a method of performing an analysis on a body fluid, by placing the collection member of the device in contact with a body fluid, allowing the collection member to collect the body fluid, and removing the barrier from between the collection member and the lateral flow member. In particular applications, the method is designed to collect oral secretions, such as saliva, by placing the device in the mouth of a test subject. In those embodiments in which a liquid sufficiency indicator is included, the barrier is not removed until the sufficiency indicator provides a signal that adequate liquid has been collected to perform the test. Once the liquid flows into the lateral flow member, a signal from the indicator(s) allows the presence, absence, and/or quantity of the analyte to be detected. In particular embodiments of the method, the test subject grasps the housing with a digit (such as the thumb) on a fingerprint receiving region of the housing, for subsequent positive identification of the test subject.
The disclosed embodiments also include a kit for detection of an analyte in a liquid, such as an oral liquid. The kit includes the collection device, and instructions for placing the device in a liquid collection cavity (such as the mouth), waiting until the collection member collects oral liquid, then removing the removable barrier.
The foregoing summary will be better understood by reference to the drawings, and the following detailed description.